1. Field of the Invention
The present invention relates generally to a laser processing apparatus and a laser processing method for processing a workpiece, and more particularly to a laser processing apparatus and a laser processing method for a semiconductor wafer including a groove forming step of applying a laser beam to the semiconductor wafer along a plurality of division lines to thereby form a plurality of laser processed grooves along these division lines on the semiconductor wafer.
2. Description of the Related Art
In a semiconductor device fabrication process, a plurality of crossing division lines called streets are formed on the front side of a substantially disk-shaped semiconductor wafer such as a silicon wafer and a gallium arsenide wafer to partition a plurality of regions where devices such as ICs and LSIs are respectively formed. The semiconductor wafer is divided into the individual devices along the division lines by using a cutting apparatus or a laser processing apparatus, and these devices are widely used in various electrical equipment such as mobile phones and personal computers. In general, a dicing apparatus is used as the cutting apparatus. The dicing apparatus includes a cutting blade having a thickness of about 30 to 300 μm. The cutting blade is obtained by bonding super abrasive grains such as diamond and CBN with metal or resin. Cutting is performed by rotating the cutting blade at a high speed of about 30000 rpm and feeding the cutting blade into a semiconductor wafer.
On the other hand, the laser processing apparatus essentially includes a chuck table for holding a semiconductor wafer, laser beam applying means for applying a pulsed laser beam to the semiconductor wafer held on the chuck table, and feeding means for relatively feeding the chuck table and the laser beam applying means. The pulsed laser beam has an absorption wavelength to the semiconductor wafer, and it is applied to the semiconductor wafer along the division lines formed on the front side of the semiconductor wafer to thereby form a plurality of laser processed grooves along these division lines. After forming the laser processed grooves, an external force is applied to the semiconductor wafer to break the semiconductor wafer along the laser processed grooves, thereby dividing the semiconductor wafer into the individual devices (see Japanese Patent Laid-open No. 2007-19252, for example).